Hello, Moreira! I have a feeling the problem is that you have both been damaged by past relationships. And I suspect he is still struggling with what's happened to him--and he shuts down because he has too many problems (some probably related to his experiences in the military) to have the emotional energy to cope with your problems.

And it is very difficult to go back to being just friends after being in a romantic relationship.

I honestly think you both could use some therapy.